1. Field of the Invention
The present invention is generally related to a gear shift assist mechanism for a sterndrive or an outboard motor and, more particularly, to the use of a hydraulic cylinder and piston arrangement that utilizes hydraulic pressure that is made available for another purpose, such as a power assisted trim or steering system, to provide a force which urges the gear selector of the sterndrive or outboard motor into forward or reverse gear in response to electrical signals associated with the manual movement of a gear selector.
2. Description of the Prior Art
Many different types of hydraulically assisted mechanisms are well known to those skilled in the art. Some of these hydraulically assisted mechanisms are used in conjunction with marine propulsion systems and marine vessels.
U.S. Pat. No. 5,340,341, which issued to Yoshimura on Aug. 23, 1994, describes a power assisted mechanism for a marine propulsion unit. The marine propulsion unit steering and gear shift system comprises a single source of hydraulic power, a steered device, a gear shift member, steering and gear shift control mechanism connected to their respective members and first and second power assist devices connected to the gear shift and steering control mechanism for power assist. A single substantially constant output hydraulic pump supplies an essentially constant level of fluid power for the first and second power assist devices to assist the operator in controlling the steering and gear shift controls.
U.S. Pat. No. 6,346,017, which issued to Silorey et al on Feb. 12, 2002, describes a gear shift mechanism for a marine outboard motor drive unit. The mechanism includes a reversible DC electric motor, a sliding clevis, and a shift rod for actuating a gearset within a gearcase between forward, reverse, and neutral positions. The mechanism is housed in a watertight gear shift cover that is attached to a trunion that, in turn, attaches to a top surface of the gearcase. Electronic, logic driven controls reverse the polarity of the motor to manipulate the shift rod via the sliding clevis to shift the gearcase into a selected operating position.
U.S. Pat. No. 5,328,396, which issued to Hayasaka on Jul. 12, 1994, describes a power transmission system for an inboard/outboard motor. A marine outboard motor having an outboard drive unit that includes a bevel gear forward, reverse transmission having hydraulically operated clutches is described. A hydraulic pump for actuating the clutches and for lubricating the transmission is driven off the rear end of the input shaft and control valve means selectively communicates the fluid from the hydraulic pump with the hydraulic clutches. The valve means is a rotary plug type valve but is constructed so as to minimize axial and radial forces acting that would tend to bind its movement. The construction of the outboard drive unit is such that the bevel gear transmission and hydraulically operated clutches can conveniently be inserted through like diameter oppositely facing openings formed in the upper end of the housing assembly of the outboard drive unit.
U.S. Pat. No. 6,338,286, which issued to Skogward et al on Jan. 15, 2002, describes a control device. The apparatus for controlling the gears of a motor vehicle comprises a pivotal gear lever for pivoting between gear positions corresponding to the gear positions for the motor vehicle transmission, a primary hydraulic piston/cylinder arrangement coupled to the gear lever, a secondary hydraulic piston/cylinder arrangement coupled to the gear box of the motor vehicle, and a hydraulic circuit hydraulically communicating with the primary and secondary hydraulic piston and cylinder arrangements and including a flow limiter valve with an open position in which the hydraulic flow of the hydraulic circuit is not limited and a plurality of closed positions for controllably limiting the hydraulic flow in the hydraulic circuit whereby movement between the various gear positions for the motor vehicle is controlled.
U.S. Pat. No. 6,202,812, which issued to Semke on Mar. 20, 2001, describes a simplified transfer case shift actuator. The actuator utilizes standard hydraulic components to achieve high neutral and low positions. A floating piston is movable within a cylinder, and abuts a spacer after a predetermined amount of movement. Once the floating piston abuts the spacer, further movement of the rod is prevented. This defines the neutral position. The use of the spacer and the floating piston provides a simplified arrangement for achieving the neutral position when compared to the prior art.
U.S. Pat. No. 5,667,052, which issued to Richardson on Sep. 16, 1997, describes a hydraulic control system for a synchronizer. The system for displaying a synchronizer into engagement with a rotating gear in a gearbox includes a hydraulic piston/cylinder unit mechanically coupled to the synchronizer, an electrically controllable pressure regulating valve for supplying hydraulic fluid to the piston/cylinder unit and an electrical control circuit acting on the pressure regulating valve to vary the pressure of the hydraulic fluid supplied to the piston/cylinder unit. In order to effect a rapid and smooth engagement of the synchronizer, the control circuit acts to increase the pressure of the hydraulic fluid supplied to the piston/cylinder unit progressively.
U.S. Pat. No. 5,307,727, which issued to Berger et al on May 3, 1994, describes a neutral to drive shift time control. In a neutral to drive shift timing control mechanism, a flow control arrangement is utilized in an electro-hydraulic control system for controlling a clutch fill period of a neutral to drive shift sequence. The hydraulic control system provides a pressure pulse of predetermined time which opens a valve to permit fluid flow to bypass an accumulator feed orifice to pressurize the clutch apply cylinder and piston to a value substantially equal to the piston return spring force without providing excess flow to the accumulator. The clutch apply pressure is then permitted to increase at a more normal rate which is controlled by the accumulator. The engagement time is determined so that the pulse time can be adjusted if the neutral to drive shift is not within a predetermined time range.
U.S. Pat. No. 4,788,821, which issued to Mienko et al on Dec. 6, 1988, describes a hydraulic shift for a motor vehicle transmission. A hydraulic apparatus for remotely controlling the operative mode selector of a motor vehicle automatic transmission is described. The apparatus comprises a master cylinder having an input member operatively connected to the transmission operative mode selection or shift lever placed at the disposal of the motor vehicle operator, and a slave cylinder mounted on or proximate the transmission casing and having an output member connected to the transmission operative mode selector, the master cylinder and the slave cylinder being placed in fluid communication through flexible conduits such that each displacement of the master cylinder piston as a result of displacement of the master cylinder input member causes a corresponding displacement of the slave cylinder piston coupled to the slave cylinder output member. The master cylinder is provided with a built-in reservoir of hydraulic fluid connected to the working chambers, one on each side of the master cylinder piston, by valved passageways permitting flow of fluid from the reservoir to the low pressure chamber and closing the high pressure chamber from the reservoir so as to compensate for slow changes in hydraulic fluid volume due to expansion and contraction. The master cylinder and the slave cylinder are pivotably and adjustably mounted to a stationary support bracket by a ball and socket arrangement having an eccentric mounting aperture.
U.S. Pat. No. 4,580,457, which issued to Ishida et al on Apr. 8, 1986, describes a manual or hydraulic gear shifting apparatus. A vehicle transmission control apparatus includes a plurality of shift members for operating a vehicle transmission; a lever adapted for movement in one sense into a plurality of positions, one end of the lever being operatively coupled to a different one of the shift members in each of the positions; the lever being further adapted for pivotal movement in response to which the one end of the lever actuates the operatively coupled shift member; a select actuator comprising a select cylinder and a select piston retained thereby, the select piston being coupled to the lever and hydraulically controlled to produce the movement thereof in the one sense; a shift actuator comprising a hydraulic cylinder and a shift piston retained thereby, the shift piston being coupled to the lever and hydraulically controlled to produce the pivotal movement thereof and a control member coupled to the lever and manually operable to produce therefore both the pivotal movement and the movement in the one sense.
U.S. Pat. No. 4,149,428, which issued to Mueller on Apr. 17, 1979, describes a hydraulic shift mechanism for transfer case with multiple path drive system. The apparatus for a transfer case that has a multiple path drive system is disclosed. It includes a neutral position, a first drive path of one speed range and a second drive path of a different speed range, the apparatus including a hydraulic cylinder assembly having piston means movable to three positions and a rod connected to the piston means and to a shift mechanism of the transfer case for moving the shift mechanism of the transfer case selectively to one of the three positions of the drive system, and a hydraulic control valve means for selectively controlling from a remote location operation of the hydraulic cylinder assembly
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
A gear shift assist mechanism for a marine propulsion device, made in accordance with the preferred embodiment of the present invention, comprises a gear shift mechanism which is alternately movable into forward, neutral, and reverse positions. It also comprises a manually operable gear position selector, a hydraulic pump, a hydraulic cylinder connected in fluid communication with the hydraulic pump, and a hydraulic piston disposed within the hydraulic cylinder. An actuator is connected to the piston and also connected to the gear shift mechanism. Movement of the piston relative to the cylinder causes the gear shift mechanism to move between selected ones of the forward, neutral, and reverse positions. A switching device is connected in fluid communication with the cylinder for conducting hydraulic pressure from the hydraulic pump into a selected region of the hydraulic cylinder in response to a signal received from the manually operable gear position selector.
In a particularly preferred embodiment of the present invention, the piston is movable to a first end of the cylinder to cause the gear shift mechanism to move into forward position when the selected region is a first region of the hydraulic cylinder and the piston is movable to a second end of the cylinder to cause the gear shift mechanism to move into the first position when the selected region is a second region of the hydraulic cylinder. The piston is movable to a central position of the cylinder to cause the gear shift mechanism to move into the neutral position when the hydraulic pressure is blocked from fluid communication with both the first and second regions. A return path to the reservoir is provided. A position biasing component, such as a pair of springs, is disposed within the cylinder to urge the piston toward a position within the cylinder which corresponds to the neutral position of the gear shift mechanism.
A pressure accumulator can be connected in fluid communication between the hydraulic pump and the switching device to provide the desired pressure and flow under all operating conditions. The gear shift mechanism can comprise a shift shaft. The hydraulic pump can be connected in fluid communication with a power steering mechanism or a power trim system of the marine propulsion system. The switching device is connected in signal communication with the manually operable gear position selector.
A preferred embodiment of the present invention can further comprise an electrical switch associated with the manually operable gear position selector and responsive to the position of the manually operable gear position selector. The electrical switch can provide the signal communication between the switching device and the manually operable gear position selector.